In many technical fields, especially civil engineering and the wire and cable industry, the requirements for fatigue strength and corrosion resistance made on the materials used are increasing. For example, in engineering, to respond to the effects of "concrete cancer," engineers are looking for ways of replacing the technically adequate, but expensive stainless steels with cheaper materials. Galvanized, plastic coated or painted steel wire and cable do not sufficiently meet this requirement, because they are subject to certain usage-related limitations, like for example, temperature, welding problems and an easily damaged or brittle exterior. Solid high-grade steel wires are too expensive or do not meet the requirements for strength and aging stability.
In a known plant that produces profile steel and steel rods with non-rusting outer coatings, bimetal billets, in which the two materials are combined metallurgically, are hot-rolled into angle steel, flat steel, square and hexagonal steel, as well as round steel in the 10-50 mm diameter range. The disadvantages of the rod material produced according to this process are its limited strength, under 660 N/mm.sup.2, the diameter range of the round steel produced, which is limited to more than 10 mm, the perfectly concentric high-grade steel coating which cannot be achieved by the rolling process and the narrow possibility of varying the thickness of the high-grade steel coating by only 20-25% by volume. Nor can this round steel be further processed into high-grade wire for wire cable.